President Bush, sitting next to China's Prime Minister Wen Jiabao in the White House, rebuked the leader of Taiwan.

Then later, his officials made the strongest commitment yet to intervening in any future conflict in the Taiwan Strait.

The administration had hoped that Prime Minister Wen's visit to the US would provide an opportunity to calm down the situation in the Taiwan Strait.

Washington's Asia watchers have been growing anxious over developments there.

The US needs Chinese support over the North Korea crisis

Taiwan's President Chen Shui-bian has said he will hold a referendum in March.

It will ask the Taiwanese people to voice their opposition to China's military posture - specifically the missiles the People's Liberation Army has deployed in Fujian province, pointed at Taiwan.

China views such a referendum as provocative.

To Beijing's ears, any referendum plan sounds as if President Chen is taking Taiwan towards an act of self determination and a formal declaration of independence from China.

Chinese threats of military force against Taiwan are once again in the air.

Status quo

What Mr Bush actually said was this: "We oppose any unilateral decision, by either China or Taiwan, to change the status quo. And the comments and actions made by the leader of Taiwan indicate that he may be willing to make decisions unilaterally that change the status quo. And we oppose that."

Prime Minister Wen reportedly thought this was "terrific".

Publicly, he said: "We very much appreciate the position adopted by President Bush towards the latest news and developments in Taiwan; that is, the attempt to resort to referendum of various kinds as excuse to pursue Taiwan independence."

Appeasement of a dictatorship simply invites further attempts at intimidation

American analysts grumble that Mr Chen seeks to provoke a crisis with China because his poll numbers go up whenever China makes threats.

But in a briefing given later by "a senior administration official", the administration scrambled to make clear it was not siding with the Communist leaders of China against Taiwan's democratically-elected president.

"I want to stress here that the president's top goal is preserving the peace in the Taiwan Strait," said the official. "We are in no way abandoning support for Taiwan's democracy or for the spread of freedom."

And he went on to give the strongest warning yet that the United States would intervene in a conflict between China and Taiwan. And it was a warning to China.

"If you try to use force or coercion against the Taiwanese," he said, "We're going to be there."

Necessary ally

But America cannot afford another regional crisis. Combat in Iraq and Afghanistan and the war on terrorism suck up executive energy and bureaucratic resources.

And America especially cannot afford a crisis involving China. The US badly needs Chinese support in dousing East Asia's number one flashpoint - North Korea and its pursuit of nuclear weapons.

Taiwan's President Chen wants a "defensive referendum"

Yet Mr Bush finds himself under pressure at home to demonstrate support for Taiwan's young democracy. This is, after all, an administration that preaches "global democratic revolution".

A group of commentators at a conservative think tank, The Project for a New American Century, on hearing President Bush's rebuke to Taiwan, immediately fired off an angry editorial by mail.

"The president's statement today is a mistake," wrote Bill Kristol, Robert Kagan and Gary Schmitt.

"Appeasement of a dictatorship simply invites further attempts at intimidation. Standing with democratic Taiwan would secure stability in East Asia. Seeming to reward Beijing's bullying will not."

Deliberate ambiguity

It is difficult to characterise what took place on Tuesday as a shift in American policy.

The Americans, since the 1970s, have sought to preserve as if in amber the strange status of Taiwan - a functioning state which does not actually ever call itself an independent country - in order to keep China from attacking the island, and thereby wrecking the East Asian security balance for a generation.

The US has always described this policy as one of deliberate "ambiguity": They "do not support" Taiwanese independence but they do not "oppose" it, go the policy mantras.

And President Bush's meeting with Prime Minister Wen Jiabao does not change that substantially.

But as of Tuesday, the Americans do "oppose" what they see as Chen Shui-bian's politicking with Taiwan's security.

The administration official acknowledged that "we're seeing developments on both sides of the Strait, forcing us to drop some of the ambiguity that has been in the policy in the past".

The United States is being pulled further into the unpredictable strategic dance between China and Taiwan. President Bush and his aides just hope it won't be them that have to take sides.